Eyewitness News on Friday was inundated with complaints from people saying they were unable to file their tax returns online.

This year's tax season ends on Friday.

Many said they were struggling to save their completed forms as the system appeared to be overloaded.

"Their systems are not working. I think their operational system is overloaded that reflects poor planning on their side again."

The South African Revenue Service said it was not experiencing any system problems despite dealing with high volumes.

It encouraged customers to file their returns earlier next year and avoid the last minute rush.

The revenue service's Adrian Lackay said it was affected by power problems in Johannesburg.

"We had to vacate the Carlton Centre office; it was running on generated power and all tax payers at the office have been issued with tickets and they can return to us at a later date," said Lackay.